We propose a series of human psychophysical experiments to answer questions in two broad areas. What are the basic mechanisms of image motion processing and what are the functional benefits. In terms of mechanism, we focus at an itermediate level of analysis, askig how the signals from elementary motion subunits combine information over time, space, and spatial scale. Our primary psychophysical task will be to discriminate the direction of motion, measuring contrast thresholds, signaltonoise ratio thresholds, and minimum displacement thresholds (Dmin). One study will obtain ratings of the perceived rigidity of moving figures. In terms of the functional benefits of motion processing, we will study 3 areas; first we will measure the precision of localization of motiondefined boundaries using a width discrimination task. Second, we will investigate motionindepth sensitivity, asking whether it can be related to monocular motion sensitivity; whether it can be altered by monoclonal motion adaptation; and whether it can be supported by a cyclopean motion stimulus which has no monocular motion information. Third, we will investigate how motion processing might play a role in recalibrating the depthfromdisparity signal.